Modular guided beam flat display device

ABSTRACT

An evacuated envelope having a plurality of spaced, parallel support walls extending between and substantially perpendicular to flat substantially parallel front and back walls to provide a plurality of parallel channels extending along the front and back walls. The front and back walls and the support walls are of an electrically insulating material, typically glass. Compressed between each of the support walls and the front wall is a metal strip which serves as the tip of the support wall and which extends along the entire length of the support wall. Each tip is tapered in thickness from a thickness substantially equal to the thickness of the support wall at the support wall to a thinner thickness at the front wall. Means is provided between each metal tip and either the support wall or the front wall to prevent movement of the tip transversely of the channels. A shadow mask extends across each of the channels and extends between the metal tips and the support walls. The shadow mask is held in proper position with respect to the phosphor screen on the inner surface of the front wall by the metal tips.

BACKGROUND OF THE INVENTION

The present invention relates to a flat panel display of the modularguided beam type, and particularly to such a display in which thecontact between the support walls and phosphor screen is minimized andgood support for a shadow mask is provided.

There has been developed a flat display device which includes anevacuated envelope having substantially flat, spaced front and backwalls and spaced, parallel support walls extending between the front andback walls. The support walls form a plurality of parallel channelsextending across the front and back walls. A gun structure extendsacross one end of the channels and is adapted to generate electrons anddirect the electrons as beams into the channels. In each of the channelsis at least one beam guide which confines the electrons in the beam asthe beam flows along the channels but which permits the beam to bedeflected toward a phosphor screen on the surface of the front wall at aplurality of points along the channel. Such a display device isdescribed in the copending application for U.S. Patent of T. O. Stanley,Ser. No. 607,492, filed Aug. 25, 1975 now U.S. Pat. No. 4,031,427,entitled "Flat Cathode Ray Tube". This type of display device will begenerally referred to as a "guided beam display device".

In the copending application for U.S. Letters Patent of C. H. Andersonet al., Ser. No. 615,353, filed Sept. 22, 1975, now U.S. Pat. No.4,028,582 entitled "Guided Beam Flat Display Device" there is shown anddescribed a type of the guided beam flat display device in which at eachpoint that the beams are deflected out of their focusing guides towardthe phosphor screen the beams in each channel are simultaneouslydeflected transversely across their respective channels to scan thescreen across the entire lateral dimension of the channels. This displaydevice includes two spaced parallel grids between the focusing guidesand the phosphor screen, one of the grids is for focusing the crosssectional area of the beams and the other grid is for accelerating thebeam toward the phosphor screen. This type of the guided beam displaydevice will be referred to as a "modular guided beam display device".For a color modular guided beam display device there are three beams ineach channel and a shadow mask extends across each channel adjacent thephosphor screen.

One problem with the modular guided beam display device is that the areaof contact between the support walls and the phosphor screen on thefront wall must be minimized so that the support walls do not obscuretoo much of the phosphor screen. For this purpose it would be desirableto have the support walls as thin as possible. However, the thickness ofthe support walls, which are typically of glass, is limited in orderthat they will provide the necessary support against the atmosphericpressure loading. The support walls cannot be made entirely of metalbecause of electrical isolation requirements within the evacuatedenvelope. Therefore, it is desirable to have a structure which willprovide the necessary support within the envelope and have a minimizedwidth, and hence, area of contact with the phosphor screen.

Another requirement in the modular guided beam flat display device iswith regard to the shadow mask. It is desirable that the device be of astructure which provides for ease of mounting the shadow mask in theenvelope at the proper distance from the phosphor screen and be heldwith great precision laterally with respect to the screen.

SUMMARY OF THE INVENTION

A display device includes an evacuated envelope having spaced,substantially parallel front and back walls and spaced, substantiallyparallel support walls extending between and substantially perpendicularto the front and back walls with the support walls forming a pluralityof parallel channels extending along the front and back walls. Aseparable metal tip is compressed between the front wall and each of thesupport walls and extends along the support wall. Each of the tips has athickness substantially equal to the thickness of the support wall atthe support wall and tapers to a thinner thickness at the front wall.Means is provided for preventing the tips from movement in a directiontransverse of the channels so as to maintain the tips in position withrespect to the support walls.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view, partially broken away of a form of thedisplay device of the present invention.

FIG. 2 is a sectional view transversely across a portion of one of thechannels of the display device.

FIG. 3 is a sectional view, partially broken away, longitudinally alonga portion of one of the channels taken along line 3--3 of FIG. 2.

FIG. 4 is a sectional view longitudinally along a portion of one of thechannels taken along line 4--4 of FIG. 2.

FIG. 5 is a sectional view along a portion of the channel taken alongline 5--5 of FIG. 2.

FIG. 6 is a sectional view similar to FIG. 1 but showing a modified formof the display device.

FIG. 7 is an enlarged view of the portion of the display device withinthe circle 7 in FIG. 6.

FIG. 8 is a sectional view taken along line 8--8 of FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, one form of a flat display device of the presentinvention is generally designated as 10. The display device 10 comprisesan evacuated envelope 12, typically of glass, having a display section14 and an electron gun section 16. The display section 14 includes arectangular, substantially flat front wall 18 which supports the viewingscreen, and a rectangular substantially flat back wall 20 in spacedparallel relation to the front wall 18. The front wall 18 and back wall20 are connected by side walls 22. The front wall 18 and back wall 20are dimensioned to provide the size of the viewing screen desired, e.g.75×100 centimeters, and are spaced apart about 2.5 to 7.5 centimeters.

A plurality of spaced, parallel support walls 24 are secured between andsubstantially perpendicular to the front wall 18 and the back wall 20.The support walls 24 extend from the gun section 16 to the opposite sidewall 22. The support walls 24 provide the desired internal support forthe evacuated envelope 12 against external atmospheric pressure anddivide the display section 14 into a plurality of parallel channels 26.

On the inner surface of the front wall 18 is a phosphor screen 28. Thephosphor screen 28 may be of any well known type presently being used incathode ray tubes, e.g. black and white or color television displaytubes. However, for a color display device, the phosphor screen 28 ispreferably formed of a plurality of spaced, parallel strips of phosphorswhich emit different colors, i.e. red, blue and green, extendinglongitudinally along the channels 26. Between the phosphor strips is ablack matrix material with a portion of the black matrix materialextending along each of the support walls 24. A metal film electrode 30is provided on the phosphor screen 28.

As shown in FIG. 2, between each of the support walls 24 and the frontwall 18 is a metal strip 32 which serves as a tip for the support walland which extends the full length of the support wall 24. Each of themetal tips 32 is of a thickness at the support wall substantially equalto the thickness of the support wall 24 and tapers to a thinnerthickness at the front wall 18. As shown in FIGS. 3 and 4, each metaltip 32 has a plurality of feet 34 projecting front and spacedlongitudinally along its thicker end surface, which feet rest againstthe support wall 24. As shown in FIG. 3, each metal tip 32 has thin,flexible web portions 36 at longitudinally spaced intervals therealong.Each of the web portions 36 is formed by two closely spaced recesses 38extending transversely across the metal tip 32, one recess extendingfrom the thicker end and the other recess extending from the thinnerend. The flexible web portions 36 serve to permit longitudinal movementof the metal tip 32 which may result from the difference in thecoefficients of thermal expansion of the metal tip 32 and the glasswalls 18 and 24.

As shown in FIG. 2, each metal tip 32 has a retainer member 40 along oneof its elongated sides, and a spring member 42 along its other elongatedside. The retainer member 40 includes a mounting strip 44 extendingalong and secured to the side of the metal tip 32 at the thicker end ofthe tip. Retainer tabs 46 extend from the mounting strip 44 atlongitudinally spaced points along the mounting strip. The retainer tabs46 extend beyond the thicker end of the metal tip 32 and engage theadjacent side of the support wall 24 as shown in FIGS. 2 and 3. Theretainer tabs 46 are positioned longitudinally between the feet 34 ofthe metal tips 32. As shown in FIG. 3, the mounting strip 44 has a thinflexible web portion 48 at longitudinally spaced points therealong topermit longitudinal movement of the mounting strip along with suchmovement of the metal tip 32. The web portions 48 are positioned at theweb portions 36 of the metal tip 32.

As shown in FIG. 4, the spring member 42 includes a mounting strip 50extending along and secured to its respective side of the metal tip 32and spring tabs 52 extending from the mounting strip 50 beyond thethicker end of the metal tip 32 and engaging the adjacent side of thesupport wall 24. The spring tabs 52 are spaced longitudinally along themounting strip 50 with each of the spring tabs 52 being positionedopposite a retainer tab 46. The mounting strip 50 has thin resilient webportions 54 at longitudinally spaced points therealong. The web portions54 are positioned at the web portions 36 of the metal tip 32 so as toallow expansion or contraction of the spring member 42 along with themetal tip 32. The spring tabs 52 engage the side of the support wall 24with sufficient force so as to pull the retainer tabs 46 tightly againsttheir respective sides of the support wall 24. Thus, the metal tips 32are held on the support walls 24 so as to prevent movement of the metaltips laterally of the channels and to properly align the thinner ends ofthe metal tips with respect to the phosphor screen 28. The metal tips 32are compressed between the front wall 18 and the support walls 24 by theatmospheric pressure loading on the envelope 12.

As shown in FIG. 2, a shadow mask 56 extends across the channels 26along substantially the entire length of the channels. The shadow mask56 extends between the support walls 24 and the metal tips 32 so as tosecured in spaced, parallel relation to the phosphor screen 28. As shownin FIG. 5, the shadow mask 56 has a plurality of openings 58therethrough spaced longitudinally along the support wall 24. The feet34 of the metal tips 32 extend through the openings 58. The shadow mask56 also has pairs of parallel, slit shaped openings 60 and 62 along eachof the metal tips 32 and between the openings 58. Each of the openings60 is adapted to receive one of the spring tabs 52 and each of theopenings 62 is adapted to receive one of the retainer tabs 46. Betweeneach pair of openings 60 and 62 is a resilient web portion 64 formed bya pair of spaced, longitudinally extending slits 66. The web 64 serve topermit expansion or contraction of the shadow mask 56. In the portionsof the shadow mask 56 between the support walls 24 are the shadow maskopenings 68. For a phosphor screen 28 made up of spaced longitudinallyextending strips, the shadow mask openings 68 are arranged inlongitudinally extending rows which correspond in number to the numberof the phosphor strips. As shown in FIG. 5, the openings 58 and 60 arelarger than the metal tip feet 34 and spring tabs 52 respectively sothat the spring tabs and metal tip feet can fit freely through theirrespective openings. However, the openings 62 are of a size and sopositioned that the retainer tabs 46 engage an edge of the openings 62so as to position the shadow mask 56 transversely with respect to thephosphor screen 28. Thus, the shadow mask openings 68 are aligned withthe phosphor screen 28.

As shown in FIG. 1, along each of the channels 26 adjacent the back wall20 is an assembly which includes a pair of electron beam focusing guidegrid plates 70, a focusing grid 72 and an acceleration grid 74 securedtogether in spaced apart parallel relation. Such an assembly and themanner of mounting it in each channel 26 is shown and described in thecopending application for Letters Patent of Z. M. Andrevski, Ser. No.775,300, filed Mar. 7, 1977, entitled "Flat Display Device With BeamGuide" .Iadd.now U.S. Pat. No. 4,101,802 .Iaddend.and in the copendingapplication for U.S. Patent of K. D. Peters, Ser. No. 783,218, filedMar. 31, 1977, entitled "Guided Beam Flat Display Device With FocusingGuide Assembly Mounting Means" .Iadd.now U.S. Pat. No.4,099,087.Iaddend.. On the surface of the support walls 24 are adeflection electrode 76 which extends between the shadow mask 56 and theacceleration grid 74 along the entire length of the channel 26.

The gun section 16 is an extension of the display section 14 and extendsalong one set of adjacent ends of the channels 26. The gun section maybe of any shape suitable to enclose the particular gun structurecontained therein. The electron gun structure contained in gun section16 may be of any well known construction suitable for selectivelydirecting beams of electrons along each of the channels. For example,the gun structure may comprise a plurality of individual guns mounted atthe ends of the channels 26 for directing separate beams of electronsalong the channels. Alternatively, the gun structure may include a linecathode extending along the gun section 16 across the ends of thechannels 26 and adapted to selectively direct individual beams ofelectrons along the channels. A gun structure of the line type isdescribed in U.S. Pat. No. 2,858,464 to W. L. Roberts, issued Oct. 28,1958, entitled "Cathode Ray Tube".

The display device 10 operates in the same manner as described in theapplication of C. H. Anderson et al, Ser. No. 615,353 now U.S. Pat. No.4,028,582. Three beams of electrons are directed into each of thechannels 26 between the focusing guide grid plates 70. Potentials areapplied to the focusing guide grid plates so as to create electrostaticforces which confine the electrons to the beams as the beams flow alongthe channels. The beams are selectively deflected toward the phosphorscreen at various points along the channels so that the beams will passthrough the shadow mask 56 and impinge on the phosphor screen. As thebeams pass between the deflection electrodes 76, a potential differenceis applied to the deflection electrodes which causes the beams to bedeflected transversely across the channels. Thus, the beams in each ofthe channels are scanned across the portion of the phosphor screen 28which extends across the respective channel so that the combined scansof the beams in all of the channels provide a complete horizontal linescan of the phosphor screen. The transverse scanning of the phosphorscreen 28 is accomplished at a plurality of points along the channels toachieve a scanning of the entire phosphor screen 28. By modulating thebeams at the gun structure, a display can be achieved on the phosphorscreen 28 which can be viewed through the front wall 18 of the displaydevice.

In the assembling of the display device 10, after the support walls 24are secured to the back wall 20 and the assemblies of the grid plates70, 72, 74 and deflection electrodes 76 are mounted in the channels 26,the shadow mask 56 can then be placed over and seated on the supportwall 24. A separate metal tip 32 is then mounted on each of the supportwalls 24 with the retainer tabs 46 extending through the openings 62 inthe shadow mask 56 and the spring tabs 52 extending through the openings60 in the shadow mask 56. The spring tabs 52 press against the sides ofthe support walls 24 so as to hold the retainer tabs 46 against theirrespective sides of the support walls 24 and against the edges of theshadow mask slots 62. This holds the metal tips 32 in position on thesupport wall 24 as well as aligns the shadow mask 56 laterally withrespect to the support walls. The front wall 18, which has the phosphorscreen 28 and metal film electrode 30 thereon can then be placed acrossthe metal tips 32 and sealed to the side walls 22 of the envelope 12.When the envelope 12 is evacuated, the external atmospheric pressurewill press the front wall 18 and back wall 20 together so that the metaltips 32 will be compressed between the front wall 18 and the supportwall 24 to firmly secure the metal tips in place.

The ends of the metal tips 32 which contact the metal film electrode 30can be made thin so as to minimize the area of contact which mayinterfere with the optical output of the phosphor screen. In fact, theend of the metal tips 32 can be made thin enough so that they can beeasily hidden by the black matrix between the rows of phosphor strips ofa color display. However, even with such a thin end portion, the metaltips 32 will withstand the forces applied by the external pressureloading. In addition, the metal tips 32 serve to secure the shadow mask56 in position with the openings in the shadow mask properly alignedwith respect to the phosphor screen 28. Although the shadow mask 56 isshown and has been described as being a single metal sheet extendingacross all of the channels 26, the shadow mask 56 may be individualmetal pieces each of a lateral width slightly greater than the lateralwidth of a channel 26 so as to extend over a portion of each of thesupport walls 24 on each side of the channel. Each of such individualpieces would have a plurality of openings 60 along one longitudinal edgeto receive the spring tabs 52 of the metal tips 32, and a plurality ofopenings 62 along the other longitudinal edge to receive the retainertabs 46 of a metal tip 32.

Referring to FIG. 6, a modification of the display device of the presentinvention is generally designated as 100. The display device 100 issubstantially the same in structure as the display device 10 shown inFIGS. 1 and 2 except for the structure of the metal tips and the mannerof holding the metal tips in position laterally. In the display device100 the metal tips 132 are similar in construction to the metal tips 32in the display device 10 except that the metal tips 132 do not includethe retainer members and spring members for holding the metal tips onthe support walls. Instead, as shown in FIG. 7 each of the metal tips132 has a groove 133 in its thinner end which groove extendslongitudinally along the entire length of the metal tip. On the innersurface of the front wall 118 are a plurality of spaced, parallel,substantially semicylindrical beads 135 of a rigid material, such asglass. The beads 135 extend longitudinally along the channels 126 witheach bead being located along a separate one of the support walls 124.Each of the beads 135 fits in the groove 133 of a metal tip 132 tolocate the metal tip 132 along its respective support wall 124 and toprevent movement of the metal tip laterally of the channels 126. Each ofthe metal tips 132 is compressed between the front wall 118 and itsrespective support wall 124 by the external atmospheric pressure load.

As shown in FIG. 8, each of the metal tips 132 has longitudinally spacedfeet 134 projecting from its thicker end. The feet 134 extend throughopenings 158 in the shadow mask 156 so as to be seated on the supportwall 124. Some of the feet 134 have a lateral dimension equal to thelateral dimension of the openings 158 in the shadow mask 156 throughwhich the feet extend so that the shadow mask 156 is aligned laterallywith respect to the phosphor screen 128 on the front wall 118. Thus, thebeads 135 on the front wall 118 align the metal tips 132 with respect tothe support walls 124, which in turn aligns the shadow mask 156 withrespect to the phosphor screen 128 on the front wall 118. Although thegrooves 133 in the metal tips 132 are shown as being rectangular incross section, they may be semicircular or any other shape which willsnuggly receive the beads 135 to properly align the metal tips and holdthem laterally in position.

.[.I.]. .Iadd.We .Iaddend.claim:
 1. A display device comprisinganevacuated envelope having spaced, substantially parallel front and backwalls and spaced, substantially parallel support walls extending betweenand substantially perpendicular to the front and back walls, saidsupport walls forming a plurality of parallel channels extending alongsaid front and back walls, a separable metal tip compressed between thefront wall and each of said support walls and extending along thesupport wall, .[.each of said tips having a thickness at the supportwall substantially equal to the thickness of the support wall andtapering to a thinner thickness at the front wall..]. and meanspreventing movement of each of said tips in a direction transversely ofthe channels so as to maintain the metal tips against the support walls.2. A display device in accordance with claim 1 in which the means forpreventing the transverse movement of each tip comprises a plurality ofretainer tabs spaced longitudinally along one side of the tip, saidretainer tabs projecting beyond .[.the thicker.]. .Iadd.one .Iaddend.endof the tip and engaging one side of the adjacent support wall and aplurality of spring tabs spaced longitudinally along the other side ofthe tip, said spring tabs projecting beyond .[.the thicker.]. .Iadd.saidone .Iaddend.end of the tip and engaging the other side of the adjacentsupport walls so that the spring tabs and retainer tabs clamp thesupport wall therebetween to hold the tip on the support wall.
 3. Adisplay device in accordance with claim .[.2.]. .Iadd.1.Iaddend.including a shadow mask extending transversely across eachchannel and fitting between the metal tips and the support walls.
 4. Adisplay device in accordance with claim 3 in which the shadow mask hasopenings therethrough through which the spring tabs and retainer tabsextend, the spring tabs extend freely through their respective openingsin the shadow mask and the retainer tabs engage an edge of theirrespective openings in the shadow mask to align the shadow mask with.[.with.]. respect to the front wall.
 5. A display device in accordancewith claim 4 in which each of the metal tips has longitudinally spacedfeet projecting from .[.its thicker.]. .Iadd.said one .Iaddend.end andthe shadow mask has openings therethrough through which the feet extendto engage the respective support wall.
 6. A display device in accordancewith claim .[.2.]. .Iadd.1 .Iaddend.in which each of the metal tips hasflexible web portions at longitudinally spaced intervals therealong. 7.A display device in accordance with claim 6 in which the shadow mask hasflexible webs in the portions thereof which extend between the metal tipand the support wall.
 8. A display device in accordance with claim 1 inwhich the means for preventing the transverse movement of the metal tipsincludes a groove in the .[.thinner.]. .Iadd.other .Iaddend.end of eachtip extending longitudinally along the tip and a separate beadprojecting from the front wall along each support wall and fitting inthe groove in the respective tip.
 9. A display device in accordance withclaim 8 including a shadow mask extending transversely across eachchannel and fitting between the support walls and the metal tips.
 10. Adisplay device in accordance with claim 9 in which each metal tip has aplurality of longitudinally spaced feet projecting from .[.itsthicker.]. .Iadd.said one .Iaddend.end and the shadow mask has openingstherethrough through which the feet extend to engage the respectivesupport walls, at least one of the feet of each metal tip engaging theedges of its respective opening in the shadow mask to align the shadowmask with respect to the front wall. .Iadd.
 11. A display device inaccordance with claim 1 in which the means for preventing the transversemovement of each tip comprises a plurality of members arranged atlongitudinally spaced points along said support walls and said metaltips, said members extending substantially perpendicular to thelongitudinal axis of said support walls and said metal tips, a portionof said members engaging one side of said support walls and said metaltips and the other portion of said members engaging the other side ofsaid support walls and said metal tips..Iaddend. .Iadd.12. A displaydevice in accordance with claim 1 in which said metal tips extendsubstantially the full length of said support walls and the edges ofsaid metal tips rest against the edges of said support walls for asubstantial portion of said lengths. .Iaddend. .Iadd.13. A displaydevice in accordance with claim 1 in which said tips have a thickness atthe support wall substantially equal to the thickness of the supportwall and a thinner thickness at the front wall. .Iaddend. .Iadd.14. Adisplay device in accordance with claim 11 in which said members extendsubstantially perpendicular to said front wall. .Iaddend.